ML20057E250
| ML20057E250 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 10/05/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20057E248 | List: |
| References | |
| NUDOCS 9310080177 | |
| Download: ML20057E250 (3) | |
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UNITED STATES iI'
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NUC, LEAR REGULATORY COMMISSION g,
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WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 83 TO FACILITY OPERATING LICENSE NO. NPF-49 EORTHEAST NUCLEAR ENERGY COMPANY. ET AL.
MILLSTONE NUCLEAR POWER STATION. UNIT NO. 3 DOCKET NO. 50-423
1.0 INTRODUCTION
By letter dated July 30, 1993, the Northeast Nuclear Energy Company (the licensee), submitted a request for changes to the Millstone Nuclear Power Station, Unit No. 3 Technical Specifications (TS). The requested changes would increase the volume requirements of the boric acid storage system of Technical Specification (TS) 3.1.2.6 in order to meet the requirements of the redesigned core for Cycle 5 operation.
2.0 EVALUATI0tj The Cycle 5 core has been redesigned due to assembly re-caging.
Re-caging involves removing the top nozzle assembly, bottom nozzle assembly and fuel rods from each assembly. The fuel rods are then "re-caged" in new skeletons having ZIRLO guide thimbles and instrumentation tubing and Zircaloy-4 mid-grids and intermediate flow mixers (IFMs). The existing top and bottom nozzle assemblies are re-used on the re-caged fuel assemblies. The re-caging resulted in shuffling 80 of the 193 fuel assemblies in the original Cycle 5 loading pattern. The redesign is necessary to prevent grid-to-grid fretting that can come about from a flow-induced vibration as experienced by other similar plants, namely Salem and Beaver Valley.
As a result of this new loading pattern, many of the core physics characteristics also have changed, which produces larger boron concentration swings from Modes 1 and 2 to Modes 4 and 5.
Although these swings are small, the licensee finds that they are sufficient to use up the small amount of margin available in the original calculation. The proposed amendment is consistent with the increased requirements as defined in the Millstone Unit 3 Cycle 5 Redesign Reload Safety Evaluation (RSE), dated July 1993 and performed by Westinghouse.
The licensee has performed evaluations of the effect of the proposed increase in volume requirements of the boric acid storage system. Specifications for Modes 1 through 4 require that enough boric acid be contained in the boric acid system to borate the plant to hot shutdown (Mode 4) and cold shutdown 5;
9310080177 931005 PDR ADOCK 05000423 p
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@ (Mode 5) from either Mode 1 or 2.
The reconfiguration of the core required an increase in the amount of boric acid to satisfy these mode changes.
The proposed change will increase the required volume in the boric acid storage system in Modes 1 through 4 from 21,020 gallons to 21,802 gallons, affecting TS 3.1.2.6 and its basis. The revised wording to the basis reflects the fact that full power and end-of-life conditions are not necessarily the most limiting conditions, consequently, the licensee introduced wording for a variety of possible limiting conditions.
The licensee conducted its redesign analysis in accordance with NRC-approved methodology (WCAP-9273-NP-A). The redesign is the result of grid-to-rod fretting findings at Salem and Beaver Valley.
In the redesign, the once-burned fuel assemblies located on the baffle were relocated inboard and fresh fuel assemblies were re-caged. The core reconfiguration made it necessary to increase the minimum limit of borated water storage.
Existing storage tanks are designed to accommodate the increase in volume, and no hardware changes or change in functioning of equipment are required.
The Millstone Unit 3 Redesign RSE demonstrated that the core reload will not adversely affect the safety of the plant. The RSE documents that the probability and conseq0ences of accidents previously evaluated in the Final Safety Analysis (FSAR) and plant system analysis (PSA) has not been increased by the redesign. Further, the redesign does not create new accidents that have not already been addressed in the FSAR.
The RSE analysis shows that the margin of safety, as defined in the Basis to the Millstone 3 TS, has not been reduced.
In all the postulated accidents analyzed, it was found that the effects were accommodated within the conservatism of the initial assumptions used in the previously applicable safety analyses. The redesign changes do not adversely affect the safety analyses for loss-of-coolant accident,(LOCAs) or other accidents. The analysis also indicated that the Cycle 5 reload will meet all applicable design criteria and ensure that all pertinent licensing basis acceptance criteria are met.
The staff has reviewed the effects of the proposed increase in the volume requirements of the boric acid storage system in order to meet the requirements of the redesigned core for Cycle 5 operation and concludes that all pertinent safety criteria are satisfactorily met.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Connecticut State official was notified of the proposed issuance of the amendment. The State official had no comments.
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4.0 ENVIRONMENTAL CONSIDERATION
The amendment changes a requirement with respect to installation or use of a j
facility component located within the restricted area as defined in 10 CFR
'l Part 20. The NRC staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that the amendment involves no significant hazards consideration, and there has been no public comment on such finding (58 FR 43928). Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR l
51.22(c)(9).
Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of-l the amendment.
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5.0 CONCLUSION
I The Commission has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety.of the l
public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common i
defense and security or to the health and safety of the public.
Principal Contributor:
A. Attard Date:
October 5,1993 I
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